Pen



FIG. 1 is a perspective of the pen;

FIG. 2 is a top view of the pen;

FIG. 3 is a front view of the pen;

FIG. 4 is a side view of the pen;

FIG. 5 is a rear view of the pen; and,

FIG. 6 is a bottom view of the pen. 

I claim the ornamental design for a pen, as shown and described. 